(a) Field of the Invention
The present invention relates to a traffic control system and method for construction work zones.
(b) Description of the Prior Art
Traffic accidents on a given section of roadway greatly increase while road work is performed in or near the roadway section. A work zone safety system is intended to reduce accidents at a construction zone. When traffic moves slowly, it is instinctive for motorists to attempt to pass slower moving vehicles in order to decrease the time of their journey. This instinct can lead to problems in a work zone because one lane is closed due to construction. In a work zone, the passing motorist will likely have difficulty re-entering traffic which may lead to an accident with another vehicle or an accident with the construction crew.
Lane restrictions, traffic speed fluctuations, bi-directional traffic flow, vehicles entering and exiting the roadway, and the general distracting surroundings of a work zone contribute to the propensity of accidents in and around roadway work zones. This propensity for accidents poses a very real risk to road construction crews, utility crews, maintenance workers, and other personnel in the vicinity of a work zone. It is not uncommon for accident rates to increase about 50% or more during times of constructions, and these accidents are increasingly causing injury and death to work zone personnel. Along with the human tragedy of the increased work zone related injuries and deaths, contractors suffer economically as well from worker""s compensation rate increases, (in Canada) increased tort liability, and decreases in worker productivity and morale as work zone personnel pay greater attention to oncoming traffic and less attention to their work assignments.
Various devices and techniques are known which attempt to alert drivers to approaching roadway hazards. These devices were designed to make drivers more aware of their surroundings and/or to reduce the speed of vehicles approaching roadway hazards. These prior art techniques included: regulatory and advisory signage; dynamic speed limit signage; mock-up police cars; high visibility clothing; and traffic flow diversion devices, to name but a few. While these prior art devices and techniques undoubtedly deterred countless additional work zone related accidents, those devices were directed solely at alerting drivers of an approaching hazard. Those devices had no way to warn work zone personnel if, or when, a vehicle strayed from a designated traffic lane and breached the work zone perimeter.
One device, however, which was well-known, attempted to signal highway workers when an errant vehicle entered the work zone. The device included an infrared signal with a reflective cone, or an ultrasonic beam, to detect a vehicle passing thereby. The infrared signal or ultrasonic beam was positioned xe2x80x9cupstreamxe2x80x9d from the work zone and was placed at about 90xc2x0 to the oncoming traffic. This detector was in communication via a wireless data link to a siren of about 120 decibel which was positioned within the work zone. When a vehicle was detected upstream, a signal was transmitted to the siren and the siren sounded an audible warning. Another embodiment of this device used a pneumatic tube which was laid across the roadway in place of the infrared or ultrasonic beam. However, the harsh environment of the roadway work zone proved too large an obstacle for this device efficiently to warn workers.
The problems with this warning device were numerous. First, most work zones were very noisy. In addition to the traffic noise and wind along any stretch of roadway, many work zones used heavy construction machinery, and jack hammers, shot blaster, and concreted cutters which create a tremendous amount of noise. Because the U.S. Occupational Safety and Health Administration (xe2x80x9cOSHAxe2x80x9d) standards required operators of this machinery to wear hearing protection, the operators were unable to hear the audible warning over the noise of the equipment they were operating and through their hearing protection. Further, even without hearing protection, personnel in the vicinity of this machinery and equipment often did not hear the audible warning.
Secondly, this warning device suffered several integrity problems. Because the device used a single detector positioned xe2x80x9cupstreamxe2x80x9d from the work zone and at about 90xc2x0 to approaching traffic, it was possible for vehicles to enter the work zone without tripping the detector. Moreover, the heat and audible noise produced by work zone equipment and passing traffic would interfere with such infrared and ultrasonic detectors, thereby causing false detections. Further, the distance between the detector and the siren necessitated a wireless data link therebetween. Modern work zones are flooded with electromagnetic noise within the popular communication frequencies. The frequent use of walkie-talkies by work zone personnel, portable and cellular telephones by work zone personnel and passing traffic, and CB and short wave radio by passing vehicular and air traffic would trigger the siren causing a significant problem with false alarms. Furthermore, this transmission required FCC compliance as well.
Other devices intended for alerting work zone personnel to vehicles breaching the work zone perimeter relied on audible alarms, despite the high level of noise which pervade the work zones, and despite OSHA regulations relating to hearing protection which substantially degraded the effectiveness of audible alarms. Although several of the devices which alerted drivers, rather than personnel, to approaching roadway hazards employed a variety of rotating and/or flashing lights to attract the drivers"" attention, such lights have never been used to convey information to the work zone personnel. This was perhaps for two reasons. Firstly, most believed that, by working in a roadway work zone where numerous flashing signs and rotating lights were present for alerting drivers to the presence of the work zone, the work zone personnel had become immune to optical warning signals, and cannot readily distinguish a typical warning light for alerting drivers from a warning light for alerting the personnel of a hazard. Secondly, because the attention of the work zone personnel was supposed to be on the task they were paid to perform, one cannot realistically have expected the worker to be looking in the direction of a warning light at all times for quickly perceiving a warning signal. For example, if a typical rotating incandescent light was used to convey the intrusion of a vehicle into the work zone, it was highly probable that a worker operating a jack hammer would be looking down and away from the light while performing this task, and thus would not perceive the warning signal at all, or at least not within sufficient time to evacuate the work zone or otherwise evade the approaching vehicle.
Generally, in the event that vehicles alternately passed on one-side road section under construction from opposite directions, traffic signals were temporarily provided at both ends of the section, thereby conducting a traffic control. One of the representative systems of such prior art was one wherein traffic signals and detector means, e.g., pressure sensors at both ends of the section were provided for detection of the number of vehicles passing therethrough, thus extending the lighting time of green signals at the heavier traffic end. A signal controller circuit included a signal device which changed indication of signals by means of vehicle detector means, e.g., light sensor or the like provided adjacent to the signals. Further, a system was disclosed for alternately switched traffic signals controller device having a set of traffic signals which was so operated that while one traffic light at passage allowed end was green, the other traffic signal at no passage allowed end was red or against and detector means were provided for detection of vehicles passing through the section. Furthermore, a traffic signal device was also provided at both ends of a road section under construction. It was, moreover, difficult to allow vehicles from opposite directions efficiently to pass the section to shorten the waiting time of vehicles. Further, according to the above prior art, the waiting time will become still comparatively long, thus easily causing traffic jams when traffic density was distinctly large at one side than at the other side in the road repairing section.
In addition, sensitive systems were employed for control of the lighting of the traffic signals based on the detection of vehicles by the detector means, e.g., pressure sensor, light sensor or the like, the control systems for traffic signals could be damaged in case of troubles in the detector means. Furthermore, as such signal systems were usually still in operation even at night when no vehicles were found, there will sometimes be no input of detection signals for more than a preset time. In such case, it cannot be concluded merely from the fact of no traffic that the detector means were out of order. Additionally, vehicles from the opposite directions will be exposed to great danger of head-on collision in the case that a vehicle enters the section against a red signal immediately after the change to red from green, while another vehicle also enters the section because of the signal change to green from red before the passing of the opposite vehicle.
Portable traffic control systems particularly suited to controlling traffic in work areas have also been disclosed. Normally, the systems were used on roads that had two traffic lanes, each lane being for traffic in a different direction. When repair work was being performed on one lane of the road, however, the traffic in both directions must use the other lane. The control systems employed traffic lights at each end of the traffic lane, alternately presenting a xe2x80x9cgoxe2x80x9d signal first to traffic from one direction and then to traffic from the other direction. The signals were viewable not only by oncoming traffic but also by an operator standing between the display units.
This warning device also suffered from several integrity problems. The heat and audible noise produced by work zone equipment, passing traffic, and other conditions of the work zone environment were capable of interfering with the infrared or ultrasonic detector in such a way that the detector could fail to detect a vehicle passing through the detection beam. Because the detector was designed to sense the presence or absence of a reflected detection beam, the detector was susceptible to detecting the heat or noise produced in the work zone as the reflected detection beam, even when the detection beam was obstructed by a vehicle entering the work zone. This was particularly true where the detector employed a continuous infrared signal, as it was difficult infrared energy. Thus, the potential always existed for a vehicle to pass through the detection beam without sounding the alarm, and without any warning to the work zone personnel.
Additionally, airborne particulate matter, birds, precipitation, and drifting debris could sporadically interrupt the constant signal or beam transmitted by the detector, thereby causing false detections which resulted in a loss of credibility for the device and costly work stoppages. Further still, the distance between the detector and the siren necessitated a wireless data link therebetween (which itself required FCC approval).
Another known device was intended to alert work zone personnel when a vehicle entered the work zone. While the earlier device employed a single detection beam that was positioned upstream from the work zone and was oriented perpendicular to oncoming traffic, the later device was configured to detect the intrusion of a vehicle into the work zone along any section of the work zone perimeter adjacent to an active traffic lane. An infrared source was placed at the beginning of the work zone which transmitted a continuous wave infrared signal along the perimeter of the work zone for reception by an infrared detector positioned downstream. If a vehicle passed between the source and the detector, thereby interrupting the continuous wave infrared signal transmitted therebetween, the detector would acknowledge this obstruction by sounding an alarm. However, this device also suffered numerous problems in operation.
Firstly, because a continuous wave infrared signal was employed, filters could not be used in the receiver to remove low frequency infrared noise without also removing the infrared signal to be detected. Nor could filters be used in the receiver electronics to remove electromagnetic noise emanating from sources within or proximate to the work zone. The range of the device was therefore unduly limited, as the detector could not be placed more than about 750 feet from the infrared source and still reliably distinguish the continuous infrared signal from other infrared energy present in the work zone. Given that typical roadway work zones have a length well in excess of about 750 feet, an unacceptably large number of infrared sources and detectors had to be used in order to detect breaching vehicles along the entire perimeter of the work zone adjacent to active traffic lanes. Moreover, because the infrared source had to transmit a focussed and narrow beam in order to have a detectable range of about 750 feet, the infrared detector had to be precisely positioned in the line of sight of the infrared source to receive the transmitted beam. The infrared detector was therefore difficult to set up and align along the work zone perimeter, and was not amenable to being moved frequently from work zone to work zone. This lack of portability was further amplified where numerous infrared sources and detectors had to be employed. The infrared detector could also be fooled into detecting a stray infrared signal as the constant infrared beam so that a vehicle could pass into the work zone undetected. Further still, this device, like all other prior art devices, employed an audible alarm for signalling personnel of an errant vehicle, the significant drawbacks of which were described above.
In addition, currently, systems which are used in controlling traffic conditions around work zones and incidents on the road are limited to the use of conventional static signs, flashing arrow signs, portable variable message signs (VMS) programmed with a single repeating message, or no signs at all. These systems provide little or no information which are useful to drivers either for avoiding the development of a traffic jam or for finding alternative routes. Though portions of the highways close to large metropolitan areas are often equipped with permanently installed VMSs and traffic signal lights designed to control the in-flow or out-flow of traffic in the highways, there are large stretches of highways that lack nay facilities for controlling the flow of traffic on the highway that are usable around work zones or incidents on the road. Rather, the same conventional equipment as described above are used and provide the same limited information to drivers. Even if permanently installed VMSs are available, current methods in the use of such devices also provide very limited information for drivers in avoiding traffic jams due to the presence of work areas and/or roadside incidents, and such information is not credible because the messages they convey are typically not appropriate to existing conditions.
Representative of the above prior art include the following patents.
U.S. Pat. No. 5,552,767,issued Sep. 6, 1996 to Toman, disclosed a warning system that alerted road system which used microwave transmitter sensor pairs positioned along the perimeter of a work zone. An optical warning device, e.g., a strobe light, was activated if the microwave beam between successive sensor pairs was broken. This patent provided an assembly for detecting and signalling when an object entered a work zone, including a plurality of transmitter sensors pairs serially connected along a section of the work zone perimeter for detecting when an object passed therethrough. Once an object was detected, an optical warning signal was activated. The optical warning signal included a primary strobe and a plurality of relay strobes positioned throughout the work zone. The primary strobe was positioned throughout the work zone, and it flashed at a predetermined flash rate which was detected by a photoelectric sensor in a nearby relay strobe. The nearby relay strobe began flashing at the predetermined flash rate thereby activating another relay strobe in close proximity. This cascading strobe effect saturated the work zone.
U.S. Pat. No. 5,610,599, issued Mar. 11, 1997 to Nomura, disclosed a traffic signal control system for use in bi-directional flow control around a construction zone. The system consisted of traffic lights at either end of the construction zone attached to a central controller. Sensors, e.g., pressure sensitive strips, were located at both ends of the construction zone and were attached to the controller. Each light was programmed with a minimum and maximum green light time. The light was initially activated for the minimum time. If heavy traffic was detected, the green light was extended for further incremental periods until the maximum time was reached. Thus, this patent provides a system for traffic signals for one-side passing. It included two-position signals temporally provided at both ends of a road repairing section through which vehicles from up lane and down lane alternately passed. Detector means were provided for detection of passage of vehicles at both ends of the road repairing section, each corresponding to each traffic signal. A sensitive controller device was provided for control of green or red lighting time and switching of red or green indication of the traffic signals based upon detection signals by the detector means. The sensitive controller was provided for cycled lighting of the traffic signals, one cycle consisting of green-red, redxe2x80x94red, red-green and redxe2x80x94red lighting in sequence of each traffic signal. A uniformly red time extension means was provided for extending the uniformly red time by a preset detection time, if a detection signal was inputted by the detector means of one traffic signal switching from green to red by the sensitive controller device within the preset detection time after such switching.
U.S. Pat. No. 5,673,039, issued Sep. 30, 1997 to Pietzch et al, disclosed a traffic and road condition monitoring system that can be disposed along a roadway. The system included multiple traffic and/or load-sensing sensors arrayed along the road to detect vehicle speed, traffic conditions, traffic violations, lane occupancy, etc. The processed output from the sensors controlled a series of flashing lights and/or alpha-numeric displays in accordance with the detected conditions. The patent thus provided an arrangement for monitoring vehicular traffic and providing information and warnings to drivers of traffic disruptions, driver error, dangerous road conditions, and severe weather. Road and traffic conditions were detected with roadside traffic sensing equipment, and the conditions were displayed over luminescent elements with signal lamps distributed at intervals along the road and combined into chains of lamps. The luminescent elements were illuminated simultaneously or in sequence for providing continuous traffic information. A processor network and a signal network were combined through a communication network to regulate the luminescent elements by processing, if necessary, under real time controlled conditions.
U.S. Pat. No. 5,661,474, issued Aug. 26, 1997 to Douglas, disclosed a construction zone intrusion detection system. The system consists of a pressure sensitive strip that was laid around the construction zone. If a vehicle passed over the strip, alarm was sounded to warn the construction crew.
U.S. Pat. No. 5,696,502, issued Dec. 9, 1997 to Busch et al, disclosed a traffic detection method using fuzzy logic to assess and predict traffic conditions dynamically. Thus, this patent provided a method of sensing traffic and detecting traffic situations on roads. Measuring points were set up for the purpose of vehicle detection using traffic sensors. A traffic data processing arrangement was provided for traffic control, at regular intervals, traffic data as vehicle speed, traffic intensity and traffic density was determine and traffic parameters determined therefrom were formed in a traffic data processing system. Two adjacent measuring points, formed a measuring section of a given length. The following traffic parameters were formed from the traffic data of two such measuring points: the speed density difference, which was calculated from the local traffic data of average speed and traffic density; a trend factor, which was formed continually from the ratio between the traffic intensities of the first and second measuring points but determined during a given period in the minute range; and the traffic intensity trend of the respective measuring point, that trend being derived on the basis of the function of the traffic intensity over the time from the increase of the tangent to the curve. The probability of a critical traffic situation was derived therefrom in a fuzzy logic.
U.S. Pat. No. 5,729,214, issued Mar. 17, 1998 to Moore, disclosed a traffic signalling system that consisted of roadside sensors for detecting traffic conditions, weather conditions, etc., a central processing station to which the detected conditions are transmitted and processed, and signals controlled by the central processing station in response to the detected conditions. This system permitted dynamic monitoring of traffic conditions, and selective display of messages to motorists depending on the conditions. This was a particularly complex system employing satellite communication of the detected conditions to a remote central processing stations.
U.S. Pat. No. 5,760,686, issued Jun. 2, 1998 to Toman, disclosed a portable warning system that alerted road construction crews to vehicles that have breached a construction perimeter. Thus, this patent disclosed an apparatus for detecting and signalling when a vehicle entered, or posed a serious risk of entering, a roadway work zone. The apparatus comprised an intrusion detector array for detecting a vehicle breaching the work zone perimeter, and a high intensity strobe light array for providing an optical warning signal when the perimeter breaching vehicle was detected. The detector array included one or more transmitters for emitting pulsed infrared signals along the work zone perimeter, and one or more receivers for detecting the presence or absence of the pulsed infrared signals. The receivers included filters for removing stray signals emanating from sources other than the transmitters. The strobe light array included a primary strobe activated by the detector array when a perimeter breaching vehicle was detected, and several relay strobes which were activated by the optical warning signal emitted by the primary strobe or another relay strobe. The primary and relay strobes emitted a high intensity, psychologically-proactive optical warning signal that was capable of immediate perception by work zone personnel despite the presence of noise and distractions. The detector array may also include a pneumatic hose assembly, and the assembly may include an electromagnetic emitter for falsely conveying the presence of a police radar trap. The electromagnetic emitter may be embodied in an excessive speed module for detecting a vehicle approaching the work zone at an excessive speed, and for activating the strobe light array upon detecting the speeding vehicle.
U.S. Pat. No. 5,900,826, issued May 4, 1996 to Farber, disclosed a signalling system for controlling two-way traffic flow around a construction zone. The system consisted of two traffic lights at opposite ends of a construction zone that were alternately activated to give a green light to oncoming traffic. The lights communicated through a wireless link. The lights were also provided with sensors that detect whether a vehicle is attempting to go through on a red light. When such a vehicle is detected, an audible warning signal is activated. Thus, this patent disclosed a portable control comprising two display units, each responsive to a transmitter""s radio signals, each display unit comprising a xe2x80x9cstopxe2x80x9d lamp and a xe2x80x9cgoxe2x80x9d lamp, the light from all lamps being viewable by a person positioned between the display units. The system was optionally equipped with an audio warning means for detecting vehicles that ignore a display unit stop light, the display units each preferably employing a simplified circuit with a servo motor mechanism.
U.S. Pat. No. 6,064,318, issued May 16, 2000 to Kirchner, III et al, disclosed a portable traffic advisory system that monitored current traffic conditions in the vicinity of a construction zone or accident. The system consisted of a plurality of wireless sensors which were positioned along the roadway to detect traffic conditions, e.g., traffic speed and density, and at least one display device that can display a variety of messages depending on the detected traffic conditions. One feature of this system was the portable and repositionable nature of the sensors and displays. This system was mainly intended to provide real time traffic information to motorists. Thus, this patent was directed to a portable system for automatic data acquisition and processing of traffic information in real-time. The system incorporated a plurality of sensors operatively positioned upstream of a work zone or roadway incident with each of the sensors being adapted to detect current traffic conditions. At least one variable message device was positioned upstream of the work zone or roadway incident. A plurality of remote station controllers were provided, each being operatively connected to the plurality of sensors and the variable message device. A central system controller was located within remote communication range of the remote station controllers. The central system controller and the plurality of remote station controllers were capable of remotely communicating with one another. Each of the sensors was adapted to output traffic condition data to its corresponding remote station controller. The corresponding remote station controllers then transmitted the traffic condition data to the central system controller. The central system controller automatically generated traffic advisory data based on the traffic condition data and transmitted the traffic advisory data to the remote station controller that was connected to the variable message device. The traffic advisory data may also be used to communicate with and control highway advisory radio transmitters and ramp metering stations. Together, one or more variable message devices, highway advisory radio transmitters and ramp metering stations may be used to inform passing motorists of traffic conditions in and around a work zone or roadway incident, and thereby control and improve the safety and efficiency of traffic operations around such sites.
(a) Aims of the Invention
Accordingly, it is a main object of the present invention to provide a system for traffic signals for one-side passing which can reduce the waiting time of vehicles and allow them efficiently to pass a road section under construction.
It is another object of the present invention to provide a system for traffic signals for one-side passing which can ensure the safety passage by vehicles in the road section at the time of signal changes.
It is yet another object of this invention to create a dynamic xe2x80x9cNO PASSINGxe2x80x9d zone based on traffic occupancy, which will change due to traffic occupancy, and which should discourage drivers from passing when the occupancy ahead is too high making merging safer.
(b) Statement of Invention
The present invention generally provides traffic monitoring and warning systems and methods, particularly for controlling suitable warning, e.g., xe2x80x9cDO NOT PASSxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d indicators immediately prior to construction zones. Dangerous and aggressive merging just before a lane restriction around a construction zone can result in accidents in the work zone, and, potentially, fatalities among the construction crews.
This invention provides a dynamic work zone safety system which includes a first traffic signalling device which is positioned along a roadside immediately upstream of a point where traffic is diverted to a single lane. The first traffic signalling device is defaulted to flash a suitable warning, e.g., xe2x80x9cDO NOT PASSxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d or similar message, thereby to provide a first xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone which is defined by the distance between the first traffic signalling device and the end of the work or construction zone. A second traffic signalling device is positioned alongside a roadside a predetermined distance upstream of the first traffic signalling device. The second traffic signalling device is defaulted not to flash a suitable warning, e.g., xe2x80x9cDO NOT PASSxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d or similar message. When activated to flash a suitable warning, e.g., xe2x80x9cDO NOT PASSxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d, (by processor means to be described hereinafter), it provides a second xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone which is contiguous to the first xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone. This lengthens the xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone to one which is between the second traffic signalling device and the end of the work or construction zone. A plurality of spaced-apart sensors is positioned along the roadway both downstream of, and upstream of, the second traffic signalling device. These sensors detect and determine the length of a traffic queue upstream of the first traffic signalling device between the first traffic signalling device and the second traffic signalling device. The sensors provide a first traffic queue signal which is representative of the length of the traffic queue. A first processor receives the first traffic queue signal and generates a first activation signal to activate the second traffic signalling device when the traffic queue reaches a predetermined length, and generates a first deactivation signal to deactivate the second traffic signal when the traffic queue is less than the predetermined length. This thereby dynamically increases or decreases the xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone.
The present invention also provides a method of traffic control for a construction work zone that assists in the prevention of dangerous merging which occurs on the approaches to work zones. The method includes establishing a first xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone immediately upstream of a construction work zone. Traffic congestion or queues are detected and measured at a plurality of locations approaching the first xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone. A processor which is loaded with suitable software determines the length of a xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone based on the detected traffic queue. Based on that determination of the length of the traffic queue, the processor automatically, by means of the software, expands or shrinks a xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone upstream of the construction work zone appropriate for the measured level of traffic.
(c) Other Features of the Invention
By a first feature of this dynamic work zone safety system of this invention, the dynamic work zone safety system includes a third traffic signalling device, such traffic signalling device being positioned alongside a roadside a predetermined distance upstream from the second traffic signalling device. The dynamic work zone safety system also provides that, when the third traffic signalling device is activated, a third xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone is created which is contiguous to the second xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone, thereby to lengthen the xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone to between the third traffic signalling device and the end of the work or construction zone. The plurality of spaced-apart sensors further includes a first plurality of spaced-apart sensors along the roadway both upstream of, and downstream of, the third traffic signalling device to detect and determine the length of a second traffic queue upstream of the first traffic signalling device between the second traffic signalling device and the third traffic signalling device, and to provide a second traffic queue signal which is representative of the second traffic queue. The processor is also configured to generate a second activation signal to activate the third traffic signalling device when the second traffic queue reaches a predetermined length, and to generate a second deactivation signal to deactivate the third traffic signalling device when the second traffic queue is less than the predetermined length, thereby dynamically increasing or decreasing the third xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone.
By a second feature of this dynamic work zone safety system of this invention, the dynamic work zone safety system includes an xe2x80x9cnthxe2x80x9d traffic signalling device, such xe2x80x9cnthxe2x80x9d traffic signalling device being positioned alongside a roadside a predetermined distance upstream from the third traffic signalling device. When the xe2x80x9cnthxe2x80x9d traffic signalling device is activated, a fourth xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone is created which is contiguous to the fourth xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone, thereby to lengthen the xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone to between the xe2x80x9cnthxe2x80x9d traffic signalling device and the end of the work or construction zone. The plurality of spaced-apart sensors still further includes a second plurality of spaced-apart sensors along the roadway both upstream of, and downstream of, the xe2x80x9cnthxe2x80x9d traffic signalling device to detect and determine the length of a third traffic queue upstream of the xe2x80x9cnthxe2x80x9d traffic signalling device between the third traffic signalling device and the xe2x80x9cnthxe2x80x9d traffic signalling device, and to provide a third traffic queue signal which is representative of the third traffic queue. That processor is also configured to generate a third activation signal to activate the xe2x80x9cnthxe2x80x9d traffic signalling device when the third traffic queue reaches a predetermined length, and to generate a third deactivation signal to deactivate the xe2x80x9cnthxe2x80x9d traffic signal when the third traffic queue is less than the predetermined length, thereby dynamically increasing or decreasing the fourth xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone.
By a first subsidiary feature of this dynamic work zone safety system of this invention and the above features of this dynamic work zone safety system of the invention, the sensors are integrated with the traffic signalling devices.
By a second subsidiary feature of this dynamic work zone safety system of this invention and the above features of this dynamic work zone safety system of the invention, the processor is connected to the traffic signalling devices wirelessly.
By a third subsidiary feature of this dynamic work zone safety system of this invention and the above features of this dynamic work zone safety system of the invention, the sensors are solar powered.
By a third subsidiary feature of this dynamic work zone safety system of the invention and the above features of this dynamic work zone safety system of the invention, the sensors are non-intrusive. Such non-intrusive sensors may be active radar sensors, or may be passive acoustic sensors, or may be ultrasonic sensors.
By a fourth subsidiary feature of this dynamic work zone safety system of this invention, and the above features of this dynamic work zone safety system, the sensors are intrusive. Examples of such intrusive sensors include a sensor which is mounted onto the roadway and which is a pneumatic road hose, a tape switch, a piezoelectric sensor, a fiber optic sensor or a quartz sensor; a passive magnetic device, an active magnetic device of an inductive loop; and an elongated elastomeric member having an elongated pressure sensor thereon, a coaxial piezoelectric cable, a flanged tube sensor with piezoelectric plates or a DYNAX(trademark) sensor.
By a third feature of this dynamic work zone safety system of this invention, and the above features of this dynamic work zone safety system, the processor is connected to the traffic signalling devices wirelessly.
By a fourth feature of this dynamic work zone safety system of this invention, and the above features of this dynamic work zone safety system, the sensors are at least one of solar powered and battery powered.
(d) Generalized Description of the Invention
The present invention thus provides a dynamic work zone safety system having multiple signals for defining a xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone, traffic sensors for detecting traffic queue length in advance of the defined xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone, and means for lengthening the xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone in response to detected traffic queue length.
In other words, the present invention provides a dynamic work zone safety system that alerts drivers that they are entering a xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone, and dynamically monitors current traffic conditions progressively to lengthen the xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone as traffic increases. For example, a first traffic signalling device is positioned along a roadside just in advance of the point where traffic tapers into a single lane. This signalling device is always activated to flash a suitable warning, e.g., xe2x80x9cDO NOT PASSxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d. A number of similar signalling devices are positioned upstream of the first signalling device. Sensors at the roadside detect traffic queue lengths, and activate successive signalling devices dynamically to lengthen the xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone. In a preferred embodiment, the sensors are integrated with the signalling devices, and are solar powered.
Accordingly, the dynamic work zone safety system of this invention is comprised of a number of roadside signalling devices, traffic sensors for detecting the length of the traffic queue, software for determining how long the xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone should be in response to the length of the detected traffic queue, and wireless communication devices that permit successive activation/deactivation of the signalling devices. The traffic sensors can also detect vehicles passing in the dynamically signed xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone, and a police officer can manually issue traffic citations for such infractions.
None of the patents discussed above suggest the expedient of dynamically lengthening a xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone.
The present invention distinguishes over the above identified U.S. Pat. No. 5,610,707 to Nomura et al, which merely describes one type of construction zone signalling system which is responsive to traffic density. Nomura et al merely increase the duration of unidirectional flow in response to heavy traffic without lengthening a xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone, while embodiments of the present invention lengthen the actual xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone.
The present invention distinguishes over the above identified U.S. Pat. No. 5,673,039 to Pietzsch et al, who merely disclose a traffic and road condition monitoring system in which the signals can be used dynamically to warn motorists of specific upcoming traffic conditions and detected traffic violations. While Pietzsch et al disclose the activation of different numbers of signals in response to different conditions, Pietzch et al does not disclose or suggest the lengthening of a xe2x80x9cNO PASSINGxe2x80x9d or xe2x80x9cMERGE LEFTxe2x80x9d or xe2x80x9cMERGE RIGHTxe2x80x9d zone in response to changes in a specific condition i.e. traffic density.